Japanese Unexamined Patent Application Publication No. 2011-230204 discloses a power tool which actuates a tool clamped and fixed to a driving shaft. In this power tool, a fork-shaped engaging portion of a swinging arm which is attached to the driving shaft engages with an outer surface of a bearing which is attached on an eccentric shaft disposed at an end of a motor shaft. When the engaging portion moves and rotates together with the eccentric shaft around the motor shaft, the swinging arm rotationally reciprocates around the driving shaft as the center of a rotation. Therefore, the driving shaft rotationally reciprocates and swings the tool around the driving shaft.